This invention relates to an efficient modular air heating solar collector which also provides excellent visibility when used as a window facade element. When used in conjunction with its control system, the present invention provides energy savings by hot air heating, by reduction of solar heat load in hot weather and by providing improved thermal insulation of the window areas in the absence of direct sunshine.
Solar energy collection for space and water heating is generally considered in terms of flat plate collectors placed on the roof of the building. The present capital costs of flat plate collectors relative to the cost of fuel which they replace precludes their use in many residential and commercial structures. Since window facade elements already include the glazing and frames, which are significant cost factors in flat plate collectors, utilizing these for the purpose of also collecting solar energy for space and water heating can significantly reduce the incremental capital cost of solar energy collection.
There has been concern over the detrimental effects of window areas on building performance for some time. The most prominent of these effects are:
(1) Large fluctuations in the solar heat loading during the day, raising the complexity and cost of air conditioning systems, PA0 (2) poor thermal insulation of window areas, resulting in large heat loss or gain when large exterior to interior temperature difference occur. PA0 (3) unacceptable glare at certain times of day and PA0 (4) rapid deterioration of fabrics and furnishings exposed to direct sunlight through windows.
Some architects have considered these disadvantages of windows to be so serious as to resort to windowless or almost windowless structures. However, the psychological benefits to the occupants provided by the visual panpramas through windows are so great windowless spaces are considered highly undesirable by most people.
Prior art contains many improvements over simple windows to overcome one or more of their drawbacks. Double pane windows with sealed space between them are commonly used to reduce heat transfer through window areas. Various screens, louvered blinds or awnings are used to reduce or eliminate glare and damage caused by direct sunlight, often at considerable expense to the see-through property of the window. Of particular relevance to the present invention, Wild (U.S. Pat. No. 3,793,931 1974) has incorporated a venetian blind between two windows in order to block glare and has added air flow means for causing air to flow out from the building interior through the space containing the louvered blind to the exterior of the building for removal of solar induced heat from the blinds to the exterior of the building. As a variation on this invention, Bourne (U.S. Pat. No. 3,971,359 1976) and Custer (U.S. Pat. No. 3,981,445 1976) teach the connection of such a louvered window structure to a central duct system which can distribute the solar generated heat throughout the building when needed. Furthermore, Fuschillo (Solar Energy vol. 17, pp 159- 165 1975) teaches various venting and window coating means whereby window areas can be used to act as solar collectors and to regulate interior temperature and lighting.
While the above references provide valuable teachings for the improved utility of window areas in buildings, the present invention provides a practical modular facade element and control system therefore which optimizes the visual and thermal efficiency of the see-through air heating solar collector.